KELNOR
Clinical safety rating
cautionComprehensive clinical and safety monograph for KELNOR (KELNOR).
Combined oral contraceptive; inhibits ovulation by suppressing gonadotropin release (FSH and LH) primarily via progestational activity; increases viscosity of cervical mucus to inhibit sperm penetration; alters endometrium.
| Metabolism | Hepatic; ethinyl estradiol is metabolized via CYP3A4; drospirenone is metabolized via CYP3A4. |
| Excretion | Primarily renal excretion of unchanged drug (70-80%) and glucuronide conjugate (10-15%); biliary/fecal elimination accounts for <5%. |
| Half-life | Terminal elimination half-life 12-15 hours; clinically relevant for once-daily dosing. |
| Protein binding | 97-99% bound primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.6-0.8 L/kg, indicating distribution into total body water. |
| Bioavailability | Oral: 85-90% due to minimal first-pass metabolism. |
| Onset of Action | Oral: 30-60 minutes; intravenous: within 5 minutes. |
| Duration of Action | Oral: 12-24 hours; intravenous: 6-12 hours depending on dose and indication. |
| Molecular Weight | 419.5 |
| Action Class | Combination Oral Contraceptive (Estrogen-Progestin) |
KELNOR (norethindrone acetate and ethinyl estradiol) is a combined oral contraceptive. Typical adult dose: 1 tablet (norethindrone acetate 1 mg/ethinyl estradiol 20 mcg) orally once daily for 21 days, followed by 7 placebo tablets, starting on day 1 of menstrual cycle.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment is recommended for renal impairment. However, use with caution in patients with impaired renal function due to potential fluid retention. |
| Liver impairment | Contraindicated in patients with Child-Pugh Class B or C (moderate to severe hepatic impairment) due to reduced clearance. Use with caution in Child-Pugh Class A (mild impairment); consider alternative contraception. |
| Pediatric use | Safety and efficacy in pediatric patients have not been established for ages <16 years (premenarchal use not indicated). For postmenarchal females aged ≥16 years, same dosing as adults. |
| Geriatric use | Not indicated for use in postmenopausal women. No specific studies in elderly; avoid in women >60 years due to increased thrombotic risk. |
| 1st trimester | Contraindicated due to risk of fetal malformations; animal studies show teratogenicity. |
| 2nd trimester | Contraindicated; may cause fetal nephrotoxicity and oligohydramnios. |
| 3rd trimester | Contraindicated; risk of neonatal renal impairment, hypotension, and skull hypoplasia. |
Clinical note
Comprehensive clinical and safety monograph for KELNOR (KELNOR).
| Placental transfer | Crosses placenta readily as evidenced by therapeutic levels in fetal cord blood. |
| Breastfeeding | Excreted into breast milk; potential for serious adverse effects in nursing infants. Use is contraindicated during breastfeeding. |
| Lactation Rating | L5 |
| Teratogenic Risk | FDA Pregnancy Category X. First trimester exposure associated with cardiovascular and neural tube defects. Second and third trimester exposure linked to fetal growth restriction and preterm delivery. |
| Fetal Monitoring | Monitor maternal blood pressure, liver function, renal function, and fetal growth via ultrasound every 4 weeks. Assess amniotic fluid index and perform nonstress testing after 28 weeks. |
| Fertility Effects | Reversible impairment of spermatogenesis in males. Females may experience menstrual irregularities. Discontinuation may restore fertility, but contraceptive counseling is mandatory due to teratogenicity. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular events from combination oral contraceptive use. Risk increases with age and heavy smoking (≥15 cigarettes/day). Women over 35 who smoke should not use combination hormonal contraceptives.
| Common Effects | Nausea, Headache, Breast tenderness, Weight gain, Irregular menstrual bleeding, Mood changes |
| Serious Effects | Venous thromboembolism (deep vein thrombosis, pulmonary embolism), Arterial thromboembolism (myocardial infarction, stroke), Hepatic adenoma or hepatocellular carcinoma, Hypertension, Gallbladder disease, Cerebral hemorrhage |
PregnancyHistory of angioedema with ACE inhibitorsBilateral renal artery stenosisHypersensitivity to drug or any component
| Precautions | Increased risk of thromboembolic disorders; liver disease; hypertension; hyperkalemia; depression; gallstone disease; glucose intolerance; fluid retention; hereditary angioedema; chloasma; monitor blood pressure and glucose. |
| Food/Dietary | No significant food interactions. High-fat meal may slightly increase absorption but not clinically relevant. Avoid grapefruit juice as it may increase estrogen levels (minor effect). Maintain consistent dietary intake of folate-rich foods if plans to conceive post-discontinuation. |
| Clinical Pearls | KELNOR (norethindrone/ethinyl estradiol) is a combined oral contraceptive. Pearl: Counsel patients to take at same time daily to maintain hormone levels and reduce breakthrough bleeding. Use backup contraception if dose missed >12 hours. Not for use in smokers >35 years due to thrombotic risk. |
| Patient Advice | Take one tablet daily at the same time, even if no intercourse. · Missing a pill increases pregnancy risk; check package insert for missed dose instructions. · Use condoms for first 7 days if starting for first time. · Watch for warning signs: severe headache, leg pain, chest pain, vision changes. · Does not protect against STIs. · Common side effects: nausea, breast tenderness, spotting, mood changes. |
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